1. Field of the Invention
The present invention relates to a liquid container having a piezo-electric device for detecting the consumption condition of a liquid in the liquid container by detecting changes in the acoustic impedance in the medium and particularly detecting changes in the resonance frequency, and a method for charging the liquid container with a liquid. Typically, the liquid container is an ink cartridge used for an ink jet recording apparatus which pressurizes ink in a pressure generation chamber in accordance with print data by a pressure generation means and injects ink drops from a nozzle opening for printing.
2. Description of the Related Art
As an example of a conventional liquid container, an ink cartridge mounted to an ink jet recording apparatus will be explained. An ink jet recording apparatus generally has a pressure generation means for pressurizing a pressure generation chamber, a carriage with an ink jet recording head having a nozzle opening for injecting pressurized ink from the ink nozzle opening as ink drops, and an ink tank for containing ink to be fed to the recording head via a flow path and is structured so as to permit continuous printing. The ink tank is generally structured as a cartridge removable from the recording apparatus so as to be simply exchanged by a user when ink is exhausted.
Further, to control ink consumption of the ink cartridge, there is a method for calculating the count of ink drops injected by the recording head and the ink amount sucked at the maintenance step of the recording head by the software and controlling ink consumption by calculation. Moreover, there is a method for attaching two electrodes for direct liquid level detection to the ink cartridge, thereby detecting the point of time when ink is actually consumed by a predetermined amount, and controlling ink consumption.
However, in the method for calculating the injection count of ink drops and the ink amount sucked by the software and controlling the ink consumption by calculation, an innegligible error is caused between the ink consumption amount by calculation and the actual consumption amount. Further, when the cartridge is removed once and then mounted again, the calculated count is reset once, so that the actual residual volume of ink cannot be found at all.
Further, in the method for controlling the point of time of ink consumption by the electrodes, the liquid-tight structure between the electrodes and the ink cartridge is complicated. Further, as a material of the electrodes, a noble metal which is highly conductive and corrosion-resistant is generally used, so that the manufacturing cost of an ink cartridge is increased. Further, the two electrodes must be mounted at separate positions respectively, so that the manufacturing steps are increased.
On the other hand, a method for detecting changes in the acoustic impedance using a piezo-electric device, thereby detecting the consumption condition of a liquid in a liquid container is proposed. By this method, the aforementioned problems are eliminated.
According to this method, the ink cartridge is mounted so that the piezo-electric device for detecting the residual quantity of ink in the cartridge comes in contact with ink in the ink cartridge.
Meanwhile, when air remains in the ink cartridge when ink is charged in the ink cartridge, a problem of defective injection of the recording head arises. However, it is not easy due to a complicated structure of the piezo-electric device to charge ink in every part in the ink cartridge free of residual air. Further, to precisely detect the consumption condition of ink in the ink cartridge by the piezo-electric device, before the ink cartridge is used first or before it is reused, it is necessary to charge the ink cartridge with ink so that ink comes in contact with the piezo-electric device. For example, in the state that the ink cartridge is charged with ink fully, when ink does not come in contact with the face of the piezo-electric device which is to come in contact with a liquid for the reason of that air bubbles remain on the face of the piezo-electric device which is to come in contact with a liquid, although the ink cartridge is fully charged with ink, the piezo-electric device detects by mistake that the ink cartridge is not charged with ink fully.
Further, recharging the used ink cartridge with ink is more difficult than charging a new ink cartridge with ink. In the used ink cartridge, ink is adhered to the part in the neighborhood of the ink feed port where fine slits and holes exist while in use and air may be shut in the slits and holes. When the ink in the ink cartridge is exhausted in this state and the ink cartridge is withdrawn, at the time of recharging the ink cartridge with ink, it is difficult to charge the slits and holes, where ink is adhered and air is shut in, with ink.
Further, in the method for detecting changes in the acoustic impedance by the piezo-electric device, thereby detecting the consumption condition of the liquid in the liquid container, the piezo-electric device is structured so as to be in contact with ink in order to detect the ink level. Therefore, if ink is consumed and the ink level is lowered below the mounting position of the piezo-electric device, when ink is adhered to the piezo-electric device by mistake due to vibration and/or swing, although there is no ink under normal state, there is a risk that the piezo-electric device may detect by mistake that there is ink. Even when ink drops are adhered to the inner wall of the ink cartridge, and the ink drops fall, and ink is adhered to the piezo-electric device, there is a possibility that the same maldetection may be caused.
Further, in a conventional ink cartridge, ink is adhered to the inner wall of the ink cartridge and the flow path, thereby ink remains, and the ink in the ink cartridge may not be used fully. The ink remaining in the ink cartridge is in contact with air for a long period of time, thus it is reduced in quality and solidified with foreign substances. When such an ink cartridge is recharged with new ink, there is the possibility that ink of poor quality and foreign substances coexist and the ink quality is reduced.
Furthermore, when a conventional ink cartridge is to be recycled, it should be fully cleaned internally. Particularly when an ink cartridge having an inner flow path in a complicated shape is to be recycled, a problem arises that the cleaning requires a lot of time and the cost is increased.
Recently, the environmental problem is a great social problem and it is very desired to provide an ink cartridge which can be easily recycled.